Last month the International Institute for Sustainable Development (IISD) reported that an international measure that aims to prevent the spread of invasive aquatic species had come into force (see the full article on the IISD website).
Large tracts of farmlands and pastures in the Amhara Regional State of Ethiopia are infested by the invasive weed parthenium (Parthenium hysterophorus). Parthenium reduces yields of major crops and replaces valuable pasture species, decreasing livestock productivity. Parthenium also makes many people sick, causing both skin and respiratory allergies, and displaces native plant species, damaging the region’s biodiversity.
In order to combat this weed, a project led by Virginia State University and funded by USAID through the Integrated Pest Management Innovation Lab at Virginia Tech has released two bioagents, the leaf-feeding beetle (Zygogramma bicolorata) and stem-boring weevil (Listronotus setosipennis). On June 20, 2017, thousands of adult Zygogramma and hundreds of Listronotus were released at several parthenium-infested sites around the town of Finote Selam.
Parthenium at time of Listronotus release, June 20, 2017
Parthenium at time of Zygogramma release, June 20, 2017
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The Fall armyworm, Spodoptera frugiperda, is a major invasive pest in Africa. It has a voracious appetite and feeds on more than 80 plant species, including maize, rice, sorghum and sugarcane. Another feature which makes it an incredibly successful invasive species is its ability to spread and reproduce quickly. CABI have developed a poster to show the life cycle of the Fall armyworm, which includes egg, 6 growth stages of caterpillar development (instars), pupa and adult moth. Click here to view the full poster, or read about the life cycle below.
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By Julien Dougoud. Reblogged from the Plantwise blog
Human health issues arising from the use of synthetic pesticides and concerns about their environmental toxicity are making lower-risk alternatives increasingly attractive. Biological control agents are living organisms which reduce harmful pest populations. Many people know of the common ladybird, whose larvae feed on aphids, but a wide range or biological control agents – e.g. predatory and parasitic insects, diseases of plant pests – are available. However, their use is still limited, in particular in low- and lower-middle-income countries. Continue reading
New research shows rates of alien species’ introduction are higher than ever. The increase in numbers of alien species does not show any sign of saturation at a global level, an international team of 45 researchers led by scientists from Senckenberg, Germany, and University of Vienna, Austria, has discovered. CABI’s Dr Marc Kenis, based in Switzerland, participated in the study as an expert in insect invasions in Europe, and the CABI Invasive Species Compendium was used as one of the main information sources for biological invasions worldwide. Continue reading
3.2 billion people are still at risk of getting malaria. Although progress has been made, if we are to achieve a 90% reduction in global malaria incidence and mortality by 2030 we must do more. Controlling invasive species may be part of the solution.
The path will not be easy. Mosquitoes are becoming increasingly resistant to pesticides – the front line of defence from malaria today. But there are other aspects we can consider, like the potential link between the incidence of malaria and invasive, non-native weeds.
It is widely known that mosquitoes need plant sugars, among other things, to survive and proliferate. Studies in Israel show that mosquitoes are much more likely (250 times more likely) to transmit malaria in areas rich in plant sugars. Could the improved management of invasive plants abundant on the African continent lead to a reduction in the incidence of malaria?
It is this question that brought together experts on malaria and plant invasions to a workshop in Kenya in December 2015, funded by the Bill & Melinda Gates Foundation. The broad objective of the workshop was to explore whether mosquitoes benefit from invasive plants and whether these plants have a positive influence on the rate of malaria transmission. The workshop also looked at whether invasive plants could be managed on a large scale.
Experts agreed that access to particular plant sugars increases the ability of Anopheles mosquitoes to transmit malaria. Although it is not known if invasive plants produce more sugars, they are more widespread and abundant than native plant species. In fact, many have the ability to invade semi-arid and arid areas, possibly increasing the prevalence of malaria in regions where mosquitoes could not survive in the past. Invasive plants also actively grow and produce flowers and fruit for longer periods than native plants, thereby extending the availability of plant sugars over longer periods than in the past. This may allow mosquitoes to retain high population numbers for much longer periods in invaded areas than in areas where there are no suitable invasive plants.
If there is an obvious link between invasive or weedy plants and Anopheles mosquitoes, can we significantly reduce the incidence of malaria by managing invasive plants?
There is no doubt that problematic plants can be controlled. Landowners, especially farmers, do it all time. The Government of South Africa allocates approximately US$120 million a year to control invasive plants, especially in water catchments, biodiversity hotspots and protected areas. It also invests in biological or natural control of invasive species. This is considered one of the most cost-effective management options, ideal for use in developing countries that do not necessarily have the resources for chemical or conventional control.
So, we can control weeds but would it reduce the incidence of malaria?
Lowering the abundance and density of any plant species favoured by Anopheles mosquitoes should lower malaria incidence. Managing many of these non-native weeds will also result in a multitude of other benefits for poor rural communities – like protecting farmland, for example.
This possible malaria-invasives linkage must be explored further. We need to do more research to fill in knowledge gaps. This includes looking at what plant species the Anopheles mosquitoes use within a given environment. Methodologies are being developed to see if rapid assessments of mosquito gut contents can provide information on what plant species they have been feeding on. We also need to look at the impact of removing certain species of invasive plants on mosquitoes. If we can compare mosquito abundance, longevity and ability to transmit malaria in areas where the invasive plant is dominant and where it is less dominant, we can build a fuller picture of the potential problem and solution.
Malaria is a terrible disease that still affects too many people. We must do all we can to understand the possible link between the incidence of malaria and invasive, non-native weeds. If a link can be found, management of invasive weeds could offer hope to many living under the threat of malaria.
By Dr Arne Witt, Coordinator, Invasive Species, CABI
For more information about CABI’s work managing invasive species, click here.
In July 2015 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc
Akebia quinata (five-leaf akebia) – a highly invasive, aggressive vine native to East Asia, A. quinata has been introduced as an ornamental to Canada, Europe, Oceania and the USA. It can outcompete native understory plants and young trees, and its dense growth can block sunlight and prevent the germination of native plants.
Geophagus brasiliensis (pearl cichlid) – an ornamental freshwater fish native to southeast Brazil, G. brasiliensis has been introduced to Australia, Florida, the Philippines and Taiwan. Its fast growth, opportunistic diet and broad environmental tolerances have allowed it to colonize new waterways, particularly artificial and disturbed habitats.
Rudbeckia laciniata (thimbleweed) – R. laciniata is an ornamental perennial plant that has been introduced to China, Japan, New Zealand and Europe. Native to eastern North America, thimbleweed grows best in bright, humid areas, such as wetlands, forest edges and roadsides. By producing lots of seeds and spreading from rhizome fragments, it can form dense monocultures which outcompete native plants.
Other invasive species datasheets recently published include: